Adaptive cancellation of co-channel CDMA interference in multipath environments
R. S. Mowbray, P.M. Grant, R.D. Pringle · 1993
Emerging receiver architectures with increasing system subscriber capacity have shown that the limitations of code division multiple access are directly attributable to the digital matched filter and are not inherent in the spread spectrum modulation format. The paper investigates one such novel receiver architecture which includes subscriber measurement to adaptively cancel the co-channel interference present and suggests a further extension of the technique to make it suitable for use in the multipath environment. An advanced software model of the proposed architecture is used to confirm the effectiveness of the new receiver in a simplified multipath environment with a number of interfering subscribers. A modification to the adaptive RAKE filter made possible through the use of intermediate signals generated by the novel receiver circuitry is also discussed and results are presented. This modified RAKE architecture will prove useful in short and medium length spreading rate systems, (<1024), where autocorrelation sidelobes often degrade the RAKE peak output signal to noise ratio.